These investigations seek to elucidate the detailed basic genetics of the filariasis vector, Culex pipiens fatigans, with the ultimate objective of developing genetic control methods. This species is cosmopolitan in distribution while filariasis is believed to affect 200 million people. Attempts to control the disease or the vector have been unsuccessful. Insecticide application generally has been inadequate and sometimes totally ineffective because of the development of insecticide resistance. Increasing pollution of the environment and harmful effects on non-target species are additional problems associated with chemical control. Future control of this species could very well lie in the genetic engineering of its hereditary material to provide a new technology of genetic manipulation of populations. The specific aims and objectives of the proposed studies are as follows: a) laboratory colonization of C.p. fatigans populations from various geographic areas: b) search for morphological and biochemical mutants and detailed investigations on their mode of inheritance, linkage relationships and cytological correlations; c) developing behavioral genetics of C.p. fatigans; d) search and evaluation of basic genetic mechanisms which can be used for biological manipulation of C.p. fatigans populations; e) bioengineering of compound stocks carrying translocations, inversions and deleterious genes to be used for genetic control.